The invention is generally directed to toner and developer compositions, and more specifically, the present invention is directed to developer and toner compositions containing therein a mixture of charge enhancing additives, which impart, or assist in imparting a positive charge to the toner resin particles and enable toners with rapid admix characteristics. In one embodiment, there are provided in accordance with the present invention toner compositions comprised of resin particles, pigment particles, and a mixture of certain charge enhancing additives enabling, for example, rapid admix of less than about 15 seconds in some embodiments, extended developer life, stable electrical properties, and compatibility with fuser rolls including Viton fuser rolls. The aforementioned toner compositions usually contain pigment particles comprised of, for example, carbon black, magnetites, cyan, magenta, yellow, blue, green, red, or brown components, thereby providing for the development of black or colored images. The toner compositions of the present invention possess excellent admix characteristics as indicated herein, and maintain their triboelectric charges for an extended number of imaging cycles exceeding, for example, 500,000. Also, the toner and developer compositions of the present invention can be selected for electrophotographic, especially xerographic, imaging and printing processes including color processes.
Developer compositions with charge enhancing additives, which impart a positive charge to the toner resin, are well known. Thus, for example, there is described in U.S. Pat. No. 3,893,935 the use of quaternary ammonium salts R.sub.4 N as charge control agents for electrostatic toner compositions. There is also described in U.S. Pat. No. 2,986,521 reversal developer compositions comprised of toner resin particles coated with finely divided colloidal silica. According to the disclosure of this patent, the development of electrostatic latent images on negatively charged surfaces is accomplished by applying a developer composition having a positively charged triboelectric relationship with respect to the colloidal silica.
Also, there are disclosed in U.S. Pat. No. 4,338,390, the disclosure of which is totally incorporated herein by reference, developer compositions containing as charge enhancing additives organic sulfate and sulfonates, which additives can impart a positive charge to the toner composition. Further, there are disclosed in U.S. Pat. No. 4,298,672 positively charged toner compositions with resin particles and pigment particles, and as charge enhancing additives alkyl pyridinium compounds. Additionally, other documents disclosing positively charged toner compositions with charge control additives include U.S. Pat. Nos. 3,944,493; 4,007,293; 4,079,014; 4,394,430 and 4,560,635.
Compositions with inner salt charge enhancing additives are illustrated in U.S. Pat. No. 4,752,550, the disclosure of which is totally incorporated herein by reference. It is indicated in column 3, beginning at line 57, that one of the objects of the invention of the '550 patent resides in providing toner compositions containing mixtures of inner salt charge enhancing additives and other known charge enhancing additives. Examples of mixtures of charge enhancing additives are illustrated in column 4, beginning at line 1, and include mixtures of the inner salts with, for example, distearyl dimethyl ammonium methyl sulfate, reference U.S. Pat. No. 4,560,635; organic sulfate and sulfonate compositions inclusive of stearyl phenethyl dimethyl ammonium tosylates, reference U.S. Pat. No. 4,338,390; and alkyl pyridinium chlorides including cetyl pyridinium chloride, reference U.S. Pat. No. 4,298,672. Advantages of the toner and developers of the '550 patent, particularly when they include therein one additive such as the inner salts, see column 9, and note the working Examples, include rapid admix, that is the toner compositions will acquire a positive charge in a period of from about 5 seconds to about 1 minute, see column 9, beginning at line 17; compatibilty with Viton fuser rolls; are lower fusing temperatures, that is from about 20.degree. F. to about 40.degree. F. than is achievable for toners and developers having incorporated therein some of the charge enhancing additives of the prior art, including quaternary ammonium salts.
As a result of a patentability search, there were located U.S. Pat. Nos. 4,560,635; 4,604,338 and 4,792,513, which patents illustrate toners with charge enhancing additives.
Moreover, toner compositions with negative charge enhancing additives are known, reference for example U.S. Pat. Nos. 4,411,974 and 4,206,064, the disclosures of which are totally incorporated herein by reference. The '974 patent discloses negatively charged toner compositions comprised of resin particles, pigment particles, and as a charge enhancing additive ortho-halo phenyl carboxylic acids. Similarly, there are disclosed in the '064 patent toner compositions with chromium, cobalt, and nickel complexes of salicylic acid as negative charge enhancing additives.
There is illustrated in U.S. Pat. No. 4,404,271 a complex system for developing electrostatic images with a toner which contains a metal complex represented by the formula in column 2, for example, and wherein ME can be chromium, cobalt or iron. Additionally, other patents disclosing various metal containing azo dyestuff structures wherein the metal is chromium or cobalt include 2,891,939; 2,871,233; 2,891,938; 2,933,489; 4,053,462 and 4,314,937. Also, in U.S. Pat. No. 4,433,040, the disclosure of which is totally incorporated herein by reference, there are illustrated toner compositions with chromium and cobalt complexes of azo dyes as negative charge enhancing additives.
Other prior art includes Japanese Publication No. 54-145542 which illustrates a negatively chargeable toner consisting of a resin, a colorant, and the charge control agent pyridoxine aliphatic acid ester; East German Patent Publication 218697 relating to liquid developers with charge control additives with structural units of Formulas (I), (II) and (III), and which contains olefinically polymerizable bonds; U.S. Pat. No. 3,850,642 relating to multilayer sensitive elements with ionizable salts, acids, esters, and surfactants as charge control agents; 2,970,802 illustrating a composition for the control of hypercholestermia, which composition consists of a nontoxic gelatin containing aluminum nicotinate; and 3,072,659 which discloses a method of preparing aluminum salts of nicotinic acid.
Although toners with charge enhancing additives are known, there continues to be a need for toners which possess many of the advantages illustrated herein. Additionally, there is a need for positive charge enhancing additives which are useful for incorporation into black or colored toner compositions. Moreover, there is a need for color toner applications with certain charge enhancing additives. There is also a need for toner compositions containing certain mixtures of charge enhancing additives, which toners possess acceptable triboelectric charging characteristics, and excellent admixing properties. Moreover, there continues to be a need for humidity insensitive positively charged toner and developer compositions. Further, there is a need for toners with a mixture of charge enhancing additives which can be easily and permanently dispersed into toner resin particles. There also is a need for positively charged black and colored toner compositions that are useful for incorporation into various imaging processes, inclusive of color xerography, as illustrated in U.S. Pat. No. 4,078,929, the disclosure of which is totally incorporated herein by reference; laser printers; and additionally, the toner compositions of the present invention are useful in imaging apparatuses having incorporated therein layered photoresponsive imaging members, such as the members illustrated in U.S. Pat. No. 4,265,990, the disclosure of which is totally incorporated herein by reference. Furthermore, there is a need for toner compositions whose triboelectric charging characteristics and admixing properties can be adjusted independently. Furthermore, there is a need for toner compositions which possess a triboelectric charge level of from about 10 to about 40 microcoulombs per gram, and preferably from about 10 to about 20 microcoulombs per gram, and admix charging times of from about 5 to 60 seconds, and preferably less than 15 seconds, as determined by a charge spectrograph, especially at low concentrations, for example less than 1 percent, and preferably less than 0.5 percent of charge enhancing additives.